The present invention relates to an ink-jet recording head, in which a piezoelectric element is formed via a vibration plate in a portion of a pressure generating chamber communicating with a nozzle orifice that ejects ink droplets, and ink droplets are ejected by displacement of the piezoelectric element. Furthermore, the present invention relates to a manufacturing method of the same and an ink-jet recording apparatus.
Two types of recording heads are put into practical use with regard to the ink-jet recording head, in which a portion of a pressure generating chamber communicating with a nozzle orifice that ejects ink droplets is constituted of a vibration plate, and the vibration plate is deformed by a piezoelectric element to pressurize ink in the pressure generating chamber, thus ink droplets are ejected from the nozzle orifice. One is a recording head using a piezoelectric actuator of longitudinal vibration mode that expands and contracts in the axis direction of the piezoelectric element, and the other one uses a piezoelectric actuator of flexural vibration mode.
The former can change volume of the pressure generating chamber by abutting an end surface of the piezoelectric element against the vibration plate, and manufacturing of a head suitable to high density printing is enabled. On the contrary, a difficult process in which the piezoelectric element is cut and divided in a comb teeth shape to make it coincide with the array pitch of the nozzle orifice and a method so that the cut and divided piezoelectric element is aligned and fixed to the pressure generating chamber is necessary, thus there is a problem of a complex manufacturing process.
On the other hand, in the latter, the piezoelectric element can be fabricated and installed on a vibration plate by a relatively simple process in which a green sheet, which is piezoelectric material, is adhered while fitting the shape thereof to the pressure generating chamber shape and is sintered. However, a certain size of vibration plate is required due to the usage of flexural vibration, thus there is a problem that high density array of the piezoelectric elements is difficult.
In order to solve the disadvantage of the latter recording head, as shown in Japanese Patent Laid-Open No. Hei 5-286131, a recording head is proposed, in which an even piezoelectric material layer is formed across the entire surface of the vibration plate by a deposition technology, the piezoelectric material layer is cut and divided into a shape corresponding to the pressure generating chamber by a lithography method, and the piezoelectric element is formed so as to be independent of another piezoelectric element for each pressure generating chamber.
According to the above-described process, a work for adhering the piezoelectric element on the vibration plate is unnecessary, and there is an advantage that not only the piezoelectric element can be fabricated and installed by accurate and simple means, lithography method, but also the thickness of the piezoelectric element can be made thin and a high-speed drive is enabled.
In such an ink-jet printing head, in general, the pressure generating chamber is formed so as to penetrate in the thickness direction of the plate by performing etching for the plate by use of a specified mask pattern from the plate surface opposite that having the piezoelectric element made thereon.
However, in such an ink-jet recording head, an error sometimes occurs in aligning the mask pattern for forming the piezoelectric element and the mask pattern for forming the pressure generating chamber, alternatively slippage of light exposure sometimes occurs due to a warp or the like of the plate where the pressure generating chamber is formed. Therefore, there is a problem that the relative positional accuracy between the piezoelectric element and the pressure generating chamber is lowered.
Moreover, in the case, for example, where a single crystal silicon substrate of a plane (110) of the plane orientation is employed as a plate, a position of the pressure generating chamber, the position being close to the vibration plate, is not stable due to variation of the vertical degree of a plane (111) thereof. Therefore, the relative positional accuracy between the piezoelectric element and the pressure generating chamber is lowered, thus causing problems of low ink ejection characteristics and low stability thereof.
Furthermore, in the case where the pressure generating chambers are arrayed in a high density, the thickness of compartment walls between the pressure generating chambers is made thin which results in lack of rigidity of the compartment walls, thus causing the problem that cross talk occurs among the pressure generating chambers.
For example, in the piezoelectric actuator of longitudinal vibration mode, a structure is conceived, in which a wide width portion is provided in a portion of the pressure generating chamber, the portion being dose to the vibration plate, and the width of portions of the pressure generating chamber other than the wide width portion is made narrow to thicken the corresponding compartment wall portions. However, in this case, an operation such as processing and pasting for the wide width portion of the pressure generating chamber is required, thus causing problems on operationality and accuracy.